1. Field of the Invention
The present invention relates to a semiconductor fabrication apparatus that fabricates semiconductor devices, and to a heat treatment technology for performing activation annealing or defect repair annealing and surface oxidization which succeed impurity doping intended to control the conductive property of a semiconductor substrate. More particularly, the invention is concerned with a heat treatment apparatus that requires the high temperature of 1200° C. or more so as to treat a semiconductor which has a substrate thereof made of silicon carbide.
2. Description of the Related Art
In recent years, introduction of a novel material having a wide band gap such as silicon carbide (SiC) (or gallium nitride (GaN)) as a material of a substrate of a power semiconductor device has been expected. Compared with silicon (Si) that is a conventional material, SiC has the wide band gap. Therefore, when SiC is used to fabricate a switching device or Schottky barrier diode that is included in an inverter or the like, a dielectric strength can be improved. In addition, since a leakage current is reduced owing to the improved dielectric strength, power saving can be achieved.
Processes for fabricating various kinds of power devices using SiC as a material of a substrate are broadly identical to those, in which Si is used as the material of the substrate, except the size or the like of the substrate. A process in which a large difference is observed between use of SiC and use of Si is a heat treatment process. The heat treatment process is represented by activation annealing that succeeds impurity ion implantation intended to control the conductive property of the substrate. In the case of a Si device, the activation annealing is performed at the temperature ranging from 800° C. to 1200° C. However, in the case of SiC, the temperature ranging from 1200° C. to 1800° C. is necessary in terms of the material property.
As an annealing apparatus, a resistance heating furnace described in, for example, Japanese Patent Application Laid-Open Publication No. 2009-32774 is known. Aside from the resistance heating furnace, an induction heating type annealing apparatus described in, for example, Japanese Patent Application Laid-Open Publication No. 2010-34481 is known.